Open-water aquaculture of the red alga Chondrus crispus in Prince Edward Island, Canada

The red alga Chondrus crispus (Irish moss) has been commercially harvested in Eastern Canada for almost 60 years. Its land-based tank aquaculture was initiated in the 1970s. In the 1990s, it became clear that production costs of these capital intensive systems were still too high for the carrageenan market but not for the production of edible seaweeds. Open-water aquacultu re of cold-temperate species of carrageenophytes, and in particular of C. c rispus, has rarely been attempted. This study re-examined the potential of the unique unattached and mostly vegetative population of C. crispus at Bas in Head, in eastern Prince Edward Island (P.E.I.), and at 5 transplant site s in western P.E.I. Basin Head plants were successfully transplanted to oth er sites, providing similar or different environmental conditions, and yiel ding comparable, or even higher, productivity. During the peak growth perio ds (May to end of June and autumn), daily growth rates (DGRs) between 3 and 4% d(-1) were recorded at Basin Head and Freeland, with some plants exceed ing 6% d(-1). Over the whole study period (May to October), DGRs between 2 and 4% d(-1) were lower than those reported for different species of Eucheu ma and Kappaphycus alvarezii; they were, however, compensated for by extrem ely high carrageenan yields (between 58.1 and 71.0% DW) during the summer m onths when nutrients (phosphorus and nitrogen) levels in seawater and algal tissue were low. The DGRs could be increased by developing culture structu res retaining fragmenting, but otherwise healthy, large distal clumps, lost with the present simple tying of plants on screens. Preliminary results de monstrated that transplantation and grow-out techniques are biologically su ccessful, and that the Basin Head population of C. crispus has significant potential for open-water aquaculture in estuaries and basins of Atlantic Ca nada.